2O8 PHYSIOLOGICAL CHEMISTRY. 



through the intestinal walls are reversed. This is the case in 

 diarrhoea because of the more rapid movement downward in 

 the intestine and because of the diminished or interrupted flow 

 from the intestine to the blood. There may be an increased 

 loss of proteins at the same time. 



The detection of traces of sugar calls for a preliminary extraction, and 

 purification of the extract from substances which might interfere with the 

 copper or analogous tests. A fermentation test is sometimes made and 

 without preliminary treatment. This depends on the spontaneous decom- 

 position of the sugar by bacteria with liberation of gas which is collected 

 and measured. Starch present gives the same result, however, but not 

 so rapidly. 



Cellulose. This is a common constituent of feces after the 

 consumption of vegetable foods. Practically no digestion of 

 cellulose takes place in the small intestine of man, but in the 

 large intestine there is sometimes a bacterial destruction. The 

 detection of cellulose is not difficult, although the methods are 

 somewhat complicated. The best of the methods depend on 

 the solution of other carbohydrates by treatment with weak 

 acid and then with alkali and finally with water. The mixture 

 is filtered and the residue washed with alcohol and ether ; it is 

 crude cellulose contaminated with a little ash and protein sub- 

 stance, both of which may be determined. The appearance 

 of cellulose in the feces has of course no pathological sig- 

 nificance. 



Gums. As these are not common articles of food they do 

 not occur usually in the feces. When they are consumed in 

 pastry and confectionery they may be found later in the feces 

 since they are not digested with readiness in many cases. 

 Some of the gums are but slightly soluble and undergo pan- 

 creatic digestion slowly. Experiments have shown that gum 

 tragacanth and gum arabic may be found in considerable 

 quantity after their consumption in bon-bons. 



NITROGEN AND THE PROTEINS. 



Nitrogen is found in the feces in many combinations. 

 Some of these represent residues from the digestive operations 



